Experimental Study Of Soil As Porous Medium For Evaporative Cooling
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Date
2019-07-01
Authors
Ganesan, Lagunesvary
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Cooling is becoming a major concern nowadays due to the increment of ambient
temperature. Soil is vastly used in passive and partially passive evaporative cooling
systems. Roof cooling, heat pipe, Zeer pot and more applications were built to use soil
as porous medium in inducing and preserving cooling. However, there are no many
literatures to justify the influence of physical property of soil on evaporative cooling.
Evaporative cooling influenced by the air humidity, air flow rate, presence of water,
heat energy availability and the physical properties of porous medium. Loam soil, sand,
gravel and small rocks were studied as a porous medium in an evaporative cooling
system. Variation in particle size influences soil porosity and permeability. The loam
soil, sand, gravel and small rocks provided 23.8%, 34.7%, 51.3% and 64.8% porosity,
while 0.02 ml/s, 0.43 ml/s, 9.77 ml/s and 12.37 ml/s permeability respectively.
Porosity and permeability influences air and water flow inside the porous medium. A
compact porous medium feasible to sustain coldness generated for period of time. The
research was continued with 1 bar to 5 bar compressed air to study the influence of
loam soil, sand, gravel and small rocks on evaporative cooling. The setup with 5 bar
compressed air performed better due to its low relative humidity and high volumetric
density. Loam soil and sand were worked greatly in 30% moisture content while
gravels and small rocks were able to work with 5% water content due to its physical
characteristics. In a comparative experiment with 10 kg soil and 30% moisture content,
the loam soil archived minimum temperatures of 16.43°C while sand, gravel, and small
rocks were 17.06°C, 17.40°C, and 18.26°C respectively. The water lost from 2 hours
of evaporation in loam soil, sand, gravel and small rocks are 0.3 kg, 0.35 kg, 0.45 kg
and 0.45 kg respectively. Higher water lost through evaporation results higher heat
lost. While the cooling rates reduces from 0.103°C/min, 0.098°C/min, 0.098°C/min,
0.096°C/min and 0.084°C/min for gravels, water, small rocks, loam soil and sand.
However, selection of the type of soil for an evaporation cooling system is based on
the requirement of the application. Loam soil and sand are the great selection for an
application that required cooling effect, thermal sustainability, and stability. While
gravels and small rocks are good for an application that required a high rate of
evaporation.